Beryl magic: watching TV while installing software

This is a screenshot of me watching TV. You'll notice that a faint overlay shows up above the TV. This overlay is the software installer displaying installation progress. Thanks to this, I don't have to interrupt neither work not pleasure to monitor long-running tasks:

How did I do this? I just dragged the installer window above the TV window, then I depressed the Alt key on my keyboard and pulled the mouse wheel down a few notches. Instant see-through window!